This is a strangely playable spell from Legends. For a single, easily splashable blue, you could trade junk to your opponent for indestructible and shrouded targets. Funny thing is, nowadays it's even better, because you can get both a big creature and an artifact creature. Kozilek, Butcher of Truth and Blightsteel Colossus? Thanks man, here's two Brass Man with their Unstable Mutations running out.

@land_comment: Actually you don't even need Draco. The card compares the cost of your creatures to each other, not to your opponent's. so you could swap Dumbrakul with Crookshank Kobolds as long as you had no creatures that cost more than {0}.

Kind of funny to use with Æther Mutation in a blue / green deck; take their highest cost creature, give them your highest cost creature, then return yours to your hand while making a lot of 1/1's. Good times.

If you have Draco on your side, you can gain control of the creature an opponent controls that has the highest mana cost. It could even be Emrakul, because this card doesn't specifically target a creature, only the player.